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How Do Projectors Work? (LCD, DLP, CRT, Overhead)


Whenever you use your projector, do you wonder how it works? 

The large images in accurate colors, the crisp texts, the sharp contrasts between light and dark colors; what makes all that happen?

Projectors have improved viewing experience for decades. Their importance stretches from formal applications to leisurely activities. 

This article gives an understanding of how projectors work. Also, you’ll learn how many different projectors exist out there. 

Projectors Explained

Projector

Simply put, projectors are devices for viewing images in an enlarged scale. 

Projectors use different technologies to create images. The one thing they have in common is that they all create these images using light! 

These devices can use a light beam to recreate your favorite pictures, movies, and other visual materials in high quality.  

Projectors have replaced TVs in many ways. For one, they use front projection which makes their applications endless. 

Many types of projectors are very mobile. Projectors can create images on any desired surface.  

Also, can you beat the appeal of life-sized images? For this reason, projectors are used in large venues like cinemas. 

Projectors can recreate visual material from various sources. Some use film; some, DVD recordings and other digital sources. 

Parts of a Projector

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Projectors come with different parts. This totally depends on their projection technology. 

Overhead projectors are the simplest kinds available. They are analog devices and include no electronic parts.

Major parts of the overhead projector are:

  • The Lamp
  • The reflector and mirror
  • The cooling fan
  • The Fresnel lens
  • An arm
  • The head

Read Overhead Projectors for more information. 

Digital projectors are more modern technology. They come with other parts and some of them are even smart. 

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Some parts of digital projectors include:

  • Color wheels and color filters: 

These are used in digital projectors. They help add color to white beams of light. 

  • Prisms: 

They include dichroic mirrors which filter white light. They reflect colored lights; red, green and blue. 

The same mirrors when inverted can be used to recombine light beams too. 

  • DMD chips and LCD panels: 

These are important parts of DLP and LCD projectors. They contain microscopic mirrors. 

The mirrors reflect or deflect colored light to create an image. Projectors with three panels or chips have better picture quality. 

Types of Projectors

Projectors come in different types. Some are analog while others are digital. They include:

  1. LCD projectors
  2. DLP projectors
  3. CRT projectors
  4. Overhead projectors
  5. Interactive projectors

In this section, we will explain the types of projectors available. We include all you need to know about how projectors work.

How Do LCD Projectors Work?

5 Minute explanation - How does an LCD projector work? #shorts

LCD projectors are digital devices. They use a form of projection technology called Liquid Cathode Display. 

LCD projectors make use of panels that contain thousands of tiny mirrors. These mirrors are called pixels. 

The mirrors are mobile; they are either in an off or on position. Depending on their position, they either reflect or deflect light.

The most advanced form of LCD projectors is the 3LCD projectors. They use a total of 3 panels to create images. 

The light beam from the source goes to dichroic mirrors. It is separated into red, blue, and green beans. 

These different beams are reflected onto the three LCD panels. One for each different hue. 

The pixels on the LCD panels either reflect or deflect the colored light. They create the image in their different hues. 

The three different versions of the image; red, blue, and green; go through a dichroic prism. 

They are recombined in the prism to form one image. This image goes through the lens and onto the screen showing millions of colors. 

LCD projectors display data from various media sources like DVDs and computers. They do not consume a lot of energy. 

Also, 3LCD projectors do not have the Rainbow Effect. They have high contrast levels.

The single-panel LCD projectors work a little differently. They may experience the Rainbow Effect. 

How Do DLP Projectors Work?

how does dlp work short

DLP projectors are a newer technology. They were first developed by Texas Instruments in 1987.

This technology is called Digital Light Processing technology. It uses a microchip that contains tiny mirrors numbering about 2 million. 

The mirrors on the DMD (digital micromirror device) chip are tilted in an off or on position. An electronic circuit determines the tilt of the individual mirrors.

In the on position, they reflect light in whatever color it comes. In the off position, they deflect the light away from the lens.

The off position is responsible for creating dark parts of pictures and videos. 

A color wheel is placed in the path of the light beam. This wheel colors the light red, blue, and green consecutively. 

The colored light falls on the DMD chip. Its mirrors reflect the light through the projector’s lens and onto the screen. 

The images are formed in different colors, but this switch is super fast. The human eye sees the RGB variations as one colorful image.

DLP projectors are susceptible to the rainbow effect. It is a visual anomaly associated with color wheels. 

DLP projectors have a three-chip variant. These have a different chip for each RGB color and do not use color wheels. 

The white light goes through a prism where it is split into three; red, blue and green. These beams go to their respective chips. 

The mirrors reflect the colored lights through a prism. This prism combines the light from the 3 chips. 

When the light goes through the lens, it is projected onto the screen as a single colorful picture.  

DLP projectors are known for color accuracy due to their many pixels. They are portable and less expensive than LCD.

Read more: What is the DLP Projection Technology?

How Do CRT Projectors Work?

Barco Graphics 801 CRT projector preview

CRT projectors are not as obsolete as many people think. They are a little less prominent due to their large sizes. 

A CRT projector uses a Cathode Ray Tube. This tube generates images with high brightness. 

The images formed are processed through three different CRT tubes. Each tube is for one color: red, green and blue. 

It also has a lens in front of it for enlarging the images. This lens focuses on the images, enlarges them and then projects them onto the screen. 

CRTs are known for brilliant picture quality. They also have advanced digitally and accept data from HDMI sources. 

They are durable; most of them have lamp lives of about 10,000 hours. They don’t lose brightness like DLPs and LCDs do over time. 

The downside to this technology is its size and high energy consumption. These make it unsuitable for use at home. 

Read more: Why are CRT projectors best?

How Do Overhead Projectors Work?

PowerPoint Demonstration: Overhead Projectors

Overhead projectors are simple devices. They use light to create images by passing it through a film. 

The content to be projected can be written, drawn, or printed on the film. You can also use other transparent materials. 

Overhead projectors make use of mirrors and lenses. These help them flip the image and enlarge it.

The light goes through the transparency and forms an image. Converging lenses ensure that the light is directed at a mirror. 

This mirror reflects the light. Naturally, the reflected beams are flipped. This ensures that the picture isn’t projected backwards. 

The flipped light beams are passed through an objective lens. It enlarges the image and directs it towards the screen. 

This type of projection used to be (and is still quite) popular in classrooms. It was also used for formal presentations. 

Overhead projectors are great for large texts, technical diagrams, and other materials that do not require a great deal of color detail. 

They do not require a lot of repairs. There are no moving parts so maintenance is relatively easy. 

How Do Interactive Projectors Work?

Epson Interactive Projector Tutorial - Digital Whiteboarding 101

Interactive projectors are highly advanced devices. They are usually UST (ultra-short throw) projectors. 

They project visual data onto the screen like regular projectors. However, there is one difference. 

Interactive projectors let you interact with your projection. They make this possible using special pens and sensors. 

The pen can be used to make changes to your projected image. You can draw or write on the image and the projector would record these changes. 

Interactive projection works in two ways:

  • DLP Interactive Projection

DLP interaction involves a special technique. Interactive DLP projectors project their own pattern onto the screen over your image.

The pen detects the patterns. The projector also uses the patterns to detect that the pen is being used and record its motion. 

The projector understands the information received and makes the required changes to the image. 

  • Infrared Interactive Projection

Infrared interaction is relatively simple. These projectors have a camera attached to them. 

This camera detects when you use the interactive pen on the screen. The pens direct infrared light at the screen. 

The action is reflected back to the main image behind the lens. Here, the changes occur. 

Sources of Light for Projection

Projection technology is impossible without light. Pictures and images are formed and projected using light. 

Different projectors use different sources of light. Older projectors used lamp bulbs.

Modern and digital projectors now embrace more lasting light sources. They use LEDs, lasers or a combination of both. 

Let’s explain the different types of projector lighting, briefly: 

1. Lamp Bulbs

Lamp Bulbs

These are glass bulbs containing mercury. They exhibit a high output of light which optimizes color.

Lamp bulbs are less expensive than other light sources. They can also be easily replaced. 

They’re becoming less popular with manufacturers due to their short lamp life. Their brightness reduces greatly with time.  

The implication is that they require constant replacement. This increases the maintenance cost of a projector. 

2. Laser Light

Laser light from a projector

Lasers project a strong beam of blue light. The strength improves picture quality and contrast. 

Projectors that use lasers are often the brightest. They have a brightness output of up to 30,000 lumens. It can be more!

This light source is expensive. However, laser projectors require little maintenance. The light output does not lose quality. 

3. LEDs

Led light from a projector

LEDs are a very durable light source. They have lamp lives of 20,000 hours and even more. 

Different LEDs produce different colors of light. There is no need to split any white light. 

LEDs are not as bright as lasers. However, they are small, light, and convenient for making portable projectors. 

What are the Applications of Projectors?

Projectors are used in different places for different purposes. They can be used to replace TVs even. 

Here are some important applications of projection technology:

Classroom Learning

Classroom Learning with Projector

Teachers and tutors use projectors in schools. They are handy tools for enlarging instructional material. 

A projector can project a diagram, chart, or other materials to make learning easier. You can also zoom in on important points. 

Business Signage/Promotion

Business Signage using projector

Digital signage involves the use of screens to display information and adverts. 

Some digital projectors have auto playback features. These enable them to project a single video repeatedly.

Most businesses use this to display adverts to their customers. Digital signage can display restaurant menus, news, calendars, and other information. 

Home Entertainment

Projectors used at home

Projectors can be used at home. They can replace TVs conveniently. You can watch TV, see movies and play games on them. 

They are better than TVs in some ways including contrast and picture size. This gives a life-sized quality to your viewing.  

Outdoor Recreation

cinema outdoor with a projector

Some outdoor activities require screen time. These activities include trips to the cinema, camping, and drive-ins. 

Projectors are great for these purposes. In cinemas, they create large and bright images for the audience 

Many projectors are built with resistance to elements. Dust and humidity outside would not damage it. 

Art Projection

Art projection

Artists have always tried to recreate art on different surfaces. With the help of projectors, pictures can be enlarged. 

This helps artists to recreate a picture on a larger scale. They use certain projectors for tracing images

Even other forms of decorative art are inclusive. Projectors can help you create art on cakes.

Company/Official Use

Projector for company use

Have you sat in on a meeting where a presentation was made? Most of the time, what you see on the screen is a projection. 

People use projectors in meetings and conferences. It helps display information, ideas, and plans to those concerned. 

Advantages of Projectors

What advantages do projectors have over TVs and other forms of visual display technology?

1. Large Image Size

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They are capable of projecting very large images. Even in a home, a projector can give you a cinema-size screen up to 120″. 

TVs have gotten larger over the years. Even then, they cannot measure up in size to a projector’s image. 

2. Conserves Space 

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You can get a projection unit for almost any space you have. Projection technology has made it possible to have small units. 

There are large ones and there are portable projectors weighing under 5lbs. These ones take up very little space.  

3. Convenient and Versatile

Due to front projection, you can project at nearly impossible angles. Images can be made on even sand like in projection mapping

Projectors are used in carnivals, parties, houses of worship, and other places that desire visual effects. 

4. Easy to Install

Projector installation

Many projectors are lightweight. They can be easily unboxed and set up. 

They come with manuals for guided installation and use. All you need is to mount the projector and the screen. 

5. Affordable

Affordable projector

Projectors are more affordable than TVs. A flat-screen HDTV would cost more than a projector that can give the same picture quality and an even larger image. 

Due to front projection, the screens are usually bright. They are the least expensive large-screen option for you. 

Disadvantages of a Projector

What are some of the things that make projectors a little inconvenient?

  • Projectors have to get regular maintenance like cleaning or replacing parts. 
  • The bigger the unit, the more expenses go into its installation.
  • Ambiance interferes with front projection so it is often better in dark rooms. 
  • Projectors may require a separate sound system because not all of them can process audio. 

FAQs

1. Can you watch TV on a projector?

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The answer to this is YES. With the right connections, you can easily watch TV on your projector. 

The question is: what kind of TV do you want to watch? Do you want regular free-to-air TV or cable TV channels?

Either way, all you need is an external TV tuner or a cable box. TV tuners give you access to free channels in your location. 

Cable boxes give you access to paid or subscription-based access to encrypted channels from your provider. 

You can connect the tuner or cable box to your projector using HDMI. The process is quite simple.

If both devices do not have matching HDMI ports, all you need is an appropriate adapter to make the connection. 

Read more: can you watch TV or how to connect to cable box

2. How do you watch movies on a projector?

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There are many ways to watch movies on your projector. You can stream movies using a streaming stick or connect to DVD players.

Streaming sticks like the Roku or Amazon fire stick are very handy. They are plugged into the projector’s HDMI port.

These sticks stream movies using Wi-Fi. As long as they’re plugged in, they draw power from the projector’s USB port. 

Find out: How to use Amazon Firestick on a Projector.

To connect your projector to a DVD player, you need a HDMI connection. You can also play the movie on your computer and connect it to your projector. 

How do you do this?

Step 1: Disconnect the projector from the power outlet. 

Step 2: Plug one end of the HDMI cable into the projector

Step 3: Plug the other end of the HDMI cable into your DVD player or computer.

Step 4: Turn on the projector. 

Step 5: Turn on the DVD player or your computer. For a computer, make sure the display output is set to HDMI. 

Go to Start > Control Panel > Sound > Playback. Select HDMI as the digital output device. 

This will activate the audiovisual functions of the HDMI port. 

Step 6: Select HDMI as the input source on the projector

Step 7: Insert your desired DVD into the player or computer. Enjoy your viewing!

3. Is it worth buying a projector?

Projectors have proven to be more cost-effective than TVs. They give you more value and screen size for your money. 

Their light technology has also improved over time. Now, many of them use lasers which give images with better contrast. 

Projectors have versatile applications too. They can be used to project images on the unlikeliest surfaces and in any location. 

In terms of maintenance, TVs are better. They require little maintenance. Projectors parts may require replacement i.e. lamps. 

Both TVs and projectors have high-resolution capacities. The difference is that projectors have the screen size to flaunt those pixels and sharp images. 

The gap between TVs and projectors is a close one. However, projectors are certainly worth their cost. 

It all comes down to what you want in a visual display; is it size, contrast, quality?  A good projector will serve you well.

4. Is DLP better than LCD?

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DLP and LCD technologies have their individual benefits. In some ways, each one is better than the other. 

LCD projectors are typically brighter. However, they have color wheels which cause the rainbow effect. 

DLP projectors have pixels in their millions. They project images in high definition and accurate colors. 

Your purpose of getting a projector may determine which is better for you. Do you need brightness, portability, or low cost?

Generally, DLP projectors are a newer technology. This means they’re often more portable, inclusive, and reliable. 

Read more: DLP vs LCD vs LED projectors

Conclusion

Projectors have come a long way since their invention. The journey is now over a century-long and there’s a lot to show for it.

These devices are a good way to get immersive viewing experiences anywhere. They rival TVs in cost and efficiency.

Thankfully, there are many technologies involved in projection. This means you can find a variant that suits you the most.   

We hope this article has given you a good understanding of how they work. If you’re interested in getting one, check out the best projectors for Netflix movies.


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